The effects of hormones on cyclic nucleotide-dependent protein kinases in intact mammalian tissues will be investigated. The compartmentalization of the cyclic nucleotides and their subunits will be determined. The substrate specificities and other physical and kinetic properties of the protein kinases will be studied. Possible evolutionary relationships of the protein kinases and their isozymes will be explored. Detailed studies of cyclic nucleotide binding and subunit interactions will be performed.